JP6502798B2 - Base material for wet friction material and method for manufacturing the same - Google Patents

Description

  The present invention relates to a wet friction material substrate that can be incorporated into a wet clutch, a wet brake, and the like, and a method of manufacturing the same.

BACKGROUND Conventionally, a wet transmission or a wet brake using a wet friction material is used for torque transmission, braking, and the like. For example, a wet transmission has a structure in which a plurality of wet friction materials and a plurality of separator plates are alternately disposed via a small clearance, and torque transmission and non-transmission are performed by pressing and separating the two. There is. In the wet transmission, lubricating oil is supplied for the purpose of reducing the friction of the wet friction material in pressure contact and separation and absorbing the frictional heat associated with the friction.
In recent years, the miniaturization of this wet transmission has been promoted in order to reduce fuel consumption, and the above-mentioned reduction in size of the wet friction material and reduction in the number of components are required. That is, there is a demand for improving the performance of a wet friction material in which the same friction performance as in the past is exhibited by the wet friction material having a smaller size and a smaller number of components.

  In order to improve the performance of the wet friction material, it is necessary to improve the performance of the base material used for the wet friction material. The wet friction material base is generally manufactured by a paper making method. That is, paper made from solid matter from a dispersion containing the necessary components such as fibers forming the base material, friction modifiers imparting frictional properties, and other fillers imparting desired properties is wet rubbed. It becomes the base material of the material. Therefore, fillers such as friction modifiers are uniformly and randomly arranged in the base material. Here, since the arrangement of the filler on the friction surface largely affects the friction characteristic, it is possible to improve the friction characteristic by arranging a large amount of filler such as a friction modifier on the friction surface. As such a technique, the following patent document 1 and the following patent document 2 are known.

JP, 2012-097360, A JP, 2011-252554, A

According to Patent Document 1 above, when a fiber material and a filler (friction modifier) are added to a solvent containing fine air bubbles and stirred, the fiber material having a large surface area moves to above the solvent, and the surface area is small. The filler moves down the solvent. A technique is disclosed that uses this phenomenon to obtain a wet friction material having a filler unevenly distributed on one side.
Further, in Patent Document 2, when water is absorbed from the slurry-like papermaking material in which the fiber material and the filler (friction modifier) are dispersed by the paper making method, the filler is controlled by controlling the water flow. There is disclosed a technique for unevenly distributing on one side of the obtained wet friction substrate.

  However, since any of the above is a technology for unevenly distributing the filler (friction modifier) during papermaking, it should be unevenly distributed so that a large amount of the friction modifier is disposed on the friction surface side in papermaking. Although it is possible to unevenly distribute only on the friction side during papermaking, when the filler in papermaking is unevenly distributed to the friction side, pores on the friction side decrease, as a result, absorption of lubricating oil is limited. As a result, it becomes difficult to obtain the desired characteristics required of the wet friction material. That is, it may be difficult to balance the uneven distribution amount and the porosity on the friction surface of the filler, and there may be cases where the balance can not be balanced depending on the required specifications.

  The present invention has been made in view of the above-mentioned prior art, and a filler, particularly a friction modifier, to be blended with a wet friction material substrate while sufficiently securing pores in the wet friction material substrate. And the like. It is an object of the present invention to provide a substrate for a wet friction material and a method of manufacturing the same, in which particulate matter such as can be significantly localized only on the friction surface.

The present invention is as follows.
The wet friction material substrate according to claim 1, comprising: a fiber layer formed by paper forming; and a particulate layer having pores formed by particulate matter on one surface of the fiber layer,
The particulate layer having pores is formed by adhering to the fibers of the one surface of the fiber layer ,
And, wherein the granulate foam is foam breaking the from foam coating layer foam composition obtained was coated on the one surface of the fibrous layer including the gist that you have obtained.
The base material for a wet friction material according to a second aspect is the base material for a wet friction material according to the first aspect, wherein a friction modifier is included as the particulate matter.
The wet friction material substrate according to claim 3 is the substrate for a wet friction material according to claim 1 or 2, wherein the thickness of the fiber layer is 0.2 mm or more and 1.3 mm or less. I assume.
In the method for producing a wet friction material according to claim 4, a foamy composition containing particulates is applied to one surface of a formed fiber layer to form a foamy coated layer containing the particulates. Forming a foamy coating layer;
And forming a granular layer having pores by breaking the foam constituting the foam-like coating layer.

  According to the wet friction material substrate, the granular layer having the fibrous layer formed by paper-making and the granular layer having pores formed by the granular material on one surface of the fibrous layer is It adheres to the fiber of one side of the said fiber layer, and is formed. That is, since the particulate matter is formed unevenly on only one surface of the fiber layer as a particulate layer having pores, the particulate matter is not present inside the fibrous layer, and is in a very prominent localized state. Further, since the particulate layer adheres to the fibers on one side of the fibrous layer, the particulate layer and the fibrous layer are not exfoliated. Therefore, since particulate matter such as a friction modifier can be unevenly distributed more remarkably than in the conventional case, particulate matter such as a friction modifier exhibiting its characteristics by being exposed on a friction surface like friction characteristics It is possible to obtain a wet friction material substrate which is condensed to a necessary surface of the wet friction material substrate, that is, the friction surface. As a result, it is possible to obtain a friction characteristic superior to that in the prior art, and to provide a wet friction material capable of coping with size reduction and reduction in the number of components. In addition, since the particulate matter such as the friction modifier is exposed to the friction surface to develop the characteristics of the particulate matter, the substrate for the wet friction material of the present invention is one side of the fiber layer of the particulate matter to be blended. Can be arranged as a granular layer having pores, and the surface of this granular layer becomes the friction surface of the wet friction material substrate, so that the arrangement inside the fiber layer where the characteristics of the granular material do not appear disappears, the granular compounded as a raw material It is possible to prevent waste of things. Furthermore, since the particulate layer having pores does not block the pores of the fiber layer, it is possible to maintain desired pores as a substrate for a wet friction material and exert desired oil absorption to the lubricating oil.

According to the method for producing a wet friction material substrate, a foamy coating layer is formed by applying a foamy composition containing particulate matter to one surface of a formed fiber layer to form a foamy coating layer. And forming a granular layer having pores by defoaming bubbles from the foam-like coating layer.
In this method, since the foam-like coating layer is foamy, the particulate matter in the foam-like coating layer can be retained on one side of the fiber layer without entering the inside of the fiber layer. Therefore, the particulate layer can be disposed only on one side of the fiber layer. Therefore, as for the granular material that expresses the characteristics by being exposed on the surface of the wet friction material substrate, the arrangement of the granular material inside the fiber layer which does not express the characteristics disappears, and waste of the granular material blended as a raw material It can prevent. And since a granular layer is obtained by breaking foam which constitutes a coating layer, it has pores. That is, even if particles such as friction modifiers are distributed only on one side of the fiber layer, the particle layer has desired pores, and the particle layer having pores is applied in a foam form to one surface of the fiber layer. Since the bubbles are formed after being bubbled, the particulate matter does not intrude into the inside of the fiber layer and does not clog the fiber layer. Accordingly, the wet friction material substrate obtained by the production method of the present invention has desired pores throughout the substrate, and can maintain desired oil absorption to the lubricating oil.

It is explanatory drawing which shows typically the cross section of the wet friction base material of this invention. It is an explanatory view shown expanding the surface of the wet friction backing material of Example 1 (300 times). It is explanatory drawing which expands and shows the surface of the wet friction base material of Example 3 (300 times). It is explanatory drawing which expands and shows the surface of the wet friction base material of the comparative example 1 (300 times).

  Hereinafter, the present invention will be described with reference to the drawings. The matter set forth herein is for the purpose of illustration and description of the embodiments of the invention and is believed to be the most effective and easily understood explanation of the principles and conceptual features of the invention. For the purpose of providing what In this respect, it is not necessary to show the structural details of the present invention that is necessary for a fundamental understanding of the present invention, but to a certain extent or more, and some forms of the present invention will be described according to the description in conjunction with the drawings. It will be clear to the person skilled in the art how is actually embodied.

[1] Base Material for Wet Friction Material The base material 1 for wet friction material of the present invention is a pore formed of particulate matter on one surface on the friction surface side of the fiber layer 11 formed by paper forming and the fiber layer 11 And a granular layer 12 having Among them, the particulate layer 12 having pores is attached to the fibers on one side of the fiber layer 11 and formed on one side of the fiber layer 11 in a desired pore state in a mode not blocking the pores 111 of the fiber layer 11 (See Figure 1).

The fiber layer 11 is a layer formed by intertwining the fibers 112 in a complicated manner by forming the fibers. Although the form of the fiber 112 is not particularly limited, for example, a length of 0.2 to 1.3 mm and a diameter of 0.1 to 10 μm are used.
Organic fibers and / or inorganic fibers can be used as the fibers 112.
Among them, as organic fibers, synthetic fibers such as polyamide fibers, polyester fibers, acrylic resin fibers and acrylic fibers, regenerated fibers such as rayon, organic natural fibers such as cellulose fibers (pulp) and the like can be mentioned. These may use only 1 type and may use 2 or more types together. Among them, polyamide-based fibers include aromatic nylon fibers and aliphatic nylon fibers, and further, aromatic nylon fibers (in particular, fibers using wholly aromatic nylon) include aramid fibers. The aramid fiber can contain either or both of para-aramid and meta-aramid.
On the other hand, as inorganic fibers, carbon-based fibers (including carbon fibers, carbonized fibers, etc.), single crystal fibers (wollastonite filler, etc.), polycrystalline fibers (alumina fibers, etc.), amorphous fibers (rock wool, glass fibers) Etc.), metal fibers and the like. These may use only 1 type and may use 2 or more types together. The blending of each fiber is made as needed.

The thickness of the fiber layer 11 is not particularly limited, but can be, for example, 0.2 mm or more and 1.3 mm or less, and more preferably 0.3 mm or more and 1.0 μm or less.
Moreover, the fiber layer 11 has the desired pore 111 according to the required specification of a wet friction material. The pores 111 are gaps between the fibers of the fiber layer 11 formed by papermaking. The presence of the gaps as the pores 111 allows the wet friction material substrate to absorb oil so as to absorb lubricating oil. As described above, the existence ratio of the pores 111 of the fiber layer 11, that is, the porosity is closely related to the oil absorption, so it is preferably 10% to 80%, and more preferably 40% to 70%. Is preferred. The porosity is calculated by immersing the base paper to be a fiber layer in oil and using the Archimedes method from the mass and volume before and after immersion. That is, assuming that the pre-immersion mass of the base paper is W ₀ (g), the post-immersion mass of the base paper is W ₁ (g), the volume of the base paper is V ₀ (cm ³ ), and the density of the oil is ρ (g / cm ³ ) The porosity of the fiber layer (%) = (W ₁ −W ₀ ) × (1 / ρ) × (1 / V ₀ ) × 100.

  The particulate layer 12 is a layer formed by the particulate matter 121. The granular layer 12 is formed by adhering to the fibers on one surface of the fiber layer 11 on the friction surface side, and is formed so as not to close the pores 111 of the fiber layer 11 described above. And it is still more preferable to form in the vicinity of the fiber of the friction surface side of the fiber layer 11 in the aspect which does not block the pore 111 of the fiber layer 11. Thus, the particulate layer 12 is formed by adhering to the fibers on the friction surface side in the vicinity of the fibers on the friction surface side, whereby the pores possessed by the granular layer 12 are one surface of the fiber layer 11 to which the particulate layer 12 adheres. The pores have a size substantially the same as that of the pores. Further, when the pores on one side of the fiber layer 11 are sufficiently large, the pores in the granular layer 12 can be made smaller than the pores on one side of the fiber layer 11. Therefore, the pores on the friction surface of the wet friction material substrate 1 prepared by adhering the granular layer to one surface of the fibrous layer, that is, the pores on the surface of the granular layer are desired in the friction surface required for the wet friction material The pores of the

  As described above, when the particulate layer 12 is formed in the vicinity of the fibers while adhering to the fibers on one side of the fiber layer 11, a more desirable pore state can be easily obtained. The particulate layer 12 having such desired pores can be obtained by breaking the foam from the foam-like coating layer obtained by applying the foam-like composition containing the particulate matter to one surface of the fiber layer 11 . That is, the granular layer 12 of the base material 1 for wet friction materials of the present invention can be obtained by including the granular material 121 in a foamy composition and coating it on one surface side of the fiber layer. Thus, the foam-like coating which applied the foamy composition in the state which suppressed that a granular material penetrates the inside of the fiber layer 11 by making the composition containing the granular material 121 into a foam and coating it. The foam is broken from the layer to form a particulate layer 12. Accordingly, the fiber layer 11 is not clogged by the particles 121 of the particle layer 12 and the pore state before the particle layer 12 is formed is maintained. As described above, in the wet friction material substrate 1 of the present invention, even if the granular layer 12 is formed in the fiber layer 11, the pore state inside the fibrous layer 11 is maintained substantially the same as the state before the granular layer is formed. The granular layer also has a substantially same pore state as that of one surface of the fiber layer 11 before forming the granular layer 12 by appropriately selecting the foam state of the foam-like composition according to the specifications required for the wet friction material, It is possible to obtain a desired pore state such as a pore state in which the pores are further reduced.

The pore state of the granular layer 12, like the pores of the fiber layer 11 described above, affects the absorption performance of the lubricating oil, which is related to the friction characteristics and the like of the wet friction material. In particular, the surface occupancy on the surface to be the friction surface of the formed granular layer 12 is important, and the value is preferably 1% or more and 60% or less.
This surface occupancy represents the ratio of the area of the particulate layer 12 covering the surface of the wet friction material substrate 1. The surface occupancy ratio was randomly selected from the surface of the wet friction material substrate 1 (the surface on which the particulate layer 12 was formed), adhesive tape {Sellotape (registered trademark)} having a size of 17 mm × 23 mm. After pasting on 5 places, peeling off, from the image analysis of the peeled surface of the 5 adhesive tapes obtained, the average value S of the total area S ₁ (cm ² ) of the non-sticking area occupied in each adhesive tape _AV (cm ² ) is calculated, and this average value S _AV (cm ² ) is calculated as a percentage (%) of the area S ₀ (cm ² = 17 mm × 23 mm) of one adhesive tape.

The particulate material 121 constituting the particulate layer 12 may be any of various materials used in the prior art, and is not particularly limited, but a friction modifier or the like exhibiting friction characteristics on the friction surface of the wet friction material substrate 1 is mentioned. Be By forming the granular layer with a friction control material or the like, since the friction control material or the like can be disposed only on the friction surface of the wet friction material substrate 1, characteristics such as friction characteristics can be easily controlled. The friction modifiers may be used alone or in combination of two or more. This makes it possible to easily impart properties such as friction properties to the friction surface of the wet friction material substrate individually or in combination.
Furthermore, specifically, the average particle diameter is preferably 0.1 μm or more and 1000 μm or less, and more preferably 2 μm or more and 200 μm or less. In addition, let the average particle diameter of a granular material be a value based on the "static image-analysis method" of JISZ8827-1.

  The thickness of the granular layer 12 is not particularly limited, but may be, for example, 0.1 μm or more and 1000 μm or less, and more preferably 2 μm or more and 400 μm or less. That is, although the granular layer 12 is bound to each other by the adhesive disposed in the foamy composition and the granular layer 12 is further adhered to the fiber layer 11 by the adhesive, it is used as a wet friction material At the same time, shear force is applied to the granular layer, so if the thickness is thick, breakage and peeling are likely to occur.

Thus, in the wet friction substrate 1 of the present invention, the particulate matter 121 can be held on one side of the fiber layer 11 without the particulate matter 121 of the particulate layer 12 being present in the fiber layer 11. Therefore, it is possible to obtain a wet friction substrate in which the particulate matter 121 is unevenly distributed only on one surface side of the fiber layer 11 more remarkably than in the prior art.
In such a form, when a friction modifier is selected as the particulate matter 121, a substantial amount of the blended friction modifier can be unevenly distributed only on one surface side of the fiber layer 11, and a small amount of friction modifier is expressed. It can be done. That is, the friction control material is intensively disposed at the most necessary place in use, ie, the friction surface, without containing an unnecessary friction control material not involved in the friction in use inside the wet friction substrate 1. Friction can be adjusted very efficiently.

  As described above, in the wet friction material substrate 1 according to the present invention, when the friction modifier is used as the particulate matter 121, the friction modifier itself is not blended in the dispersion during paper making, and the friction adjustment is performed afterward. By coating only the amount necessary to obtain the desired properties of the material, the granular layer 12 is formed on the friction surface side on the fiber layer 11.

  In the wet friction material substrate 1 of the present invention, the granular layer 12 is formed by applying a foamy composition containing the particulate matter 121 to one surface of the fiber layer 11 from a foamy coating layer Included are those obtained by breaking the foam. In this granular layer 12, the foam has already disappeared in the obtained state, and therefore, it is known that the foam was interposed in the manufacturing process, the structure or characteristics of the wet friction material substrate 1 having the granular layer 12. It is technically impossible to specify and directly specify the structure or characteristics of the wet friction material substrate by analysis. In addition, even if it is possible to analyze the structure or characteristics by any method, the cost of the operation to be identified is extremely excessive for performing the identification work in view of the need for promptness etc. in the nature of the patent application. It will take some time. That is, there are impossible and unpractical situations in directly specifying the structure or characteristics of the wet friction material substrate.

[2] Method of Manufacturing Base Material for Wet Friction Material The method of manufacturing the base material 1 for wet friction material of the present invention comprises a foam-like coating layer forming step and a bubble-breaking step. The step of forming a foamy coating layer and the step of defoaming may be performed simultaneously, or the step of defoaming may be performed after completing the step of forming a foamy coating layer.

  Among these, the foam-like coating layer forming step is a step of applying a foam-like composition containing the particulate matter 121 to the surface of the formed fiber layer 11 to form a foam-like coating layer.

The foamy composition refers to one obtained by frothing the composition containing the particulate matter 121. In the composition, a main material containing at least particulates, a foaming agent, and an adhesive is dispersed in a liquid medium (water, organic solvent, etc.), and if necessary, the main material is a thickener, a dispersing agent Etc. are dispersed in a liquid solvent. The foamy composition is obtained by foaming the composition with a foaming agent.
Among these, the foaming agent is a component that promotes the formation of bubbles, and specifically, various surfactants can be used. The adhesive is a component that adheres the fibers and particles of the fiber layer and bonds the particles. Specifically, water-soluble polymers such as polyvinyl ether, polyvinyl alcohol, polyvinyl acetate, and water-soluble acrylic polymers can be used.

The particulates are selected to give the desired properties on the fiber layer, and various materials used in the prior art can be used.
There are no particular limitations on the composition of the particulate matter and the foaming agent, but when the friction modifier is selected for the particulate matter, for example, 5% by mass or more and 40% by mass or less of the particulate matter and 5% by mass or more and 20% by mass or less of the foaming agent It can be a percentage. By being in this range, the particulate layer effectively exerts a friction adjusting function, and further, peeling from the fiber layer and breakage of the particulate layer hardly occur, and the long-term use of the wet friction material becomes possible.
The order of blending these components is not limited, and for example, a liquid in which necessary materials are batch-blended may be bubbled or various components may be added while foaming.

  Furthermore, when preparing the foamy composition, it is preferable to control the ratio of the average diameter of the foam of the foamy composition to the average particle size of the granules, as necessary. 0.005 or more and 0.5 or less are preferable, and, as for the ratio of the average particle diameter of the granular material to the average diameter of a bubble, 0.01 to 0.5 or less are more preferable. When the ratio of the average diameter of the foam of the foamy composition to the average particle diameter of the particles is less than 0.005, the average particle diameter of the particles is equal to or less than that of the particles. When the ratio of the average particle size of the foam of the foamy composition to the average particle size of the particulate matter exceeds 0.5, the foam is less likely to be formed. Here, as described above, the average particle diameter of the particulate matter is preferably 0.1 μm to 1000 μm, and more preferably 2 μm to 200 μm. On the other hand, 20 micrometers or more and 500 micrometers or less are preferable, and, as for the average diameter of a bubble, 30 micrometers or more and 300 micrometers or less are still more preferable. The average diameter of the bubbles was obtained by measuring the diameters of 50 randomly selected bubbles in the recorded image (measured on the recorded image) using the recorded image recorded through an optical microscope. It is a value.

Such a foamy composition is applied to one surface of the fiber layer 12 by the foamy coating layer forming step. And the application is performed by appropriately selecting various coating methods. Specifically, the composition can be coated by applying a foamy composition to a coating roller and pressing the roller against the fiber layer 12. Moreover, it can coat by coating using a coater.
Further, the amount of the foam-like composition applied to the fiber layer 11 is sufficient at a small amount of 1 to 10% by mass, and a substrate for a wet friction material having good friction characteristics with such a small amount of application Become. And a foamy coating layer formation process can be implemented in the wet stage before making the paper layer 11 dried, and the drying stage after drying.
Thus, in the foam-like coating layer forming step of applying the foam-like composition to the fiber layer 11, the foam-like composition does not permeate into the inside of the fiber layer 11 because the coating layer to be formed is foamy. Can be attached to the fibers of the surface of the fiber layer 11 as a cross-shaped coating layer and can be retained on the surface of the fiber layer 11. Moreover, the foam-like coating layer is in a state in which the particulate matter 121 is included in the boundary portion between the plurality of bubbles constituting the foam-like coating layer. And since the foam-like composition contains an adhesive, the adhesive adheres to the surface of the particulate matter. When the foam is broken in this state, the particulates 121 are bonded together by the adhering adhesive to form the particulate layer 12. At this time, the bound particles are not all bound, but the presence of the foam results in partially unbonded portions. The granular layer 12 has pores because the part where the binding is inhibited becomes pores. And since the granular layer 12 is formed without penetrating into the fiber layer 11, the pores 111 of the fibrous layer 11 are not blocked by the granular material 121, and the pores 111 can be maintained. Thus, the oil absorption of the wet friction material substrate 1 with respect to the lubricating oil is maintained by the pore formation of the granular layer 12 and the pore maintenance of the fiber layer 11.

The foam breaking step is a step of breaking the foam constituting the foam-like coating layer to form the particulate layer 12.
In the bubbling step, bubbling may be performed in any manner. Specifically, the foam can be naturally broken by leaving it to stand. In addition, it can be broken by heating. Furthermore, bubbles can be broken by pressure. Also, the foam can be broken by pressing. These foam-breaking methods may be used alone or in combination of two or more.

  The surface (the surface opposite to the surface attached to one surface of the fiber layer 11 in the particle layer 12) of the particle layer 12 formed by the cell-breaking process is the friction surface of the wet friction material substrate 1, and the friction surface The area ratio of the granular layer to occupy becomes the above-mentioned surface occupancy. As described above, the surface occupancy is preferably in the range of 1% to 60%. Within this range, the oil absorption property of the lubricating oil is sufficiently maintained, whereby a good wet friction material substrate 1 having good friction characteristics on the friction surface can be obtained.

Hereinafter, the present invention will be specifically described by way of examples.
[1] Preparation of Example Article A wet friction material substrate of Example 1-2 was prepared.
(1) Preparation of foamy composition 10% by mass of an alkyl ether-based foaming agent, 10% by mass of a polyvinyl ether-based adhesive, 20% by mass of an organic friction modifier (particulate matter), 60% by mass of water of a liquid solvent Were mixed to obtain a liquid of 100% by mass in total. By stirring and mixing the obtained liquid, the mixed solution becomes a foamy composition by the action of the alkyl ether-based foaming agent.
The blending amount of the foaming agent is preferably in the range of 5% by mass to 30% by mass. When the amount of the foaming agent is less than 5% by mass, the amount of bubbles is insufficient, and when it exceeds 30% by mass, the coating property is reduced.
The blending amount of the adhesive is preferably in the range of 5% by mass to 30% by mass. If the blending amount of the adhesive is less than 5% by mass, there is a concern that adhesion with the substrate can not be obtained, and if it exceeds 30% by mass, the coatability is reduced.
The blending amount of the particulate matter is preferably in the range of 5% by mass to 40% by mass. If the amount of the granular material is less than 5% by mass, there is a concern that the desired friction characteristics can not be obtained, and if it exceeds 40% by mass, the coatability is reduced.
(2) Foam-Like Coating Layer Forming Step In Example 1, the coating amount of fibers is applied to one surface of the fiber layer 11 formed by applying the foam-like composition obtained in the above (1) to a roller for coating The foam-like coating layer was formed on the fiber layer 11 by applying 0.16% by mass in Example 2 and 4 times that in Example 1 so as to be 0.04% by mass with respect to the layer 11. In the present embodiment, the fiber layer 11 is used in a state of being dried in advance.
In addition, the above-mentioned application quantity (Example 1: 0.04 mass%, Example 2: 0.16 mass%, Example 3: 0.16 mass%) is a granular layer to the sum total of a granular layer and a fiber layer. Mean the mass ratio of (particulate layer / (particulate layer + fiber layer)).
(3) Bubble-breaking step The foam-like coating layer obtained in the above (2) was allowed to stand as it was, and it was waited for the bubbles to break naturally, thereby forming the granular layer 12.
(4) Confirmation of Surface State A digital image in which the surface of the granular layer 11 of Example 1 formed by the above steps was enlarged 300 times with an optical microscope was recorded, and a part of it was shown in FIG. Here, according to image analysis, the surface occupancy by the particulate matter 121 on the friction surface of the wet friction material substrate 1 of the particulate layer 12 attached to the fiber layer 11 was 8%.

A wet friction material substrate of Example 3 was prepared.
(1) Preparation of non-foaming composition Component obtained by removing the foaming agent from the foamy composition used in Example 1, that is, 10% by mass of polyvinyl ether adhesive, 20% by mass of organic friction modifier, liquid 70% by mass of water as a solvent was mixed to obtain a coating dispersant (non-foamy composition) for forming a particulate layer.
(2) Granular layer formation process The non-foamy composition obtained in the above (1) is coated on one surface of the fiber layer using a coating roller at a coating amount of 0.16% by mass as in the example product. A granular layer was formed.
(3) Confirmation of Surface State A digital image in which the surface of the granular layer obtained in the above (2) was magnified 300 times with an optical microscope was recorded, and a part thereof is shown in FIG.

[2] Preparation of Comparative Example A wet friction material base of Comparative Example 1 was prepared.
<1> Comparative Example 1
(1) Preparation of base material for wet friction material: 20% by mass of the same organic type friction modifier as in the example is compounded in the dispersion for forming the fiber and paper-formed, and the same base material for wet friction material as in the prior art Obtained.
(2) Confirmation of Surface Condition As in Example 1, a digital image in which the surface of the wet friction material substrate was enlarged 300 times with an optical microscope was recorded, and a part of it was shown in FIG.

[3] Evaluation of base material for wet friction material <1> Measurement of static friction coefficient μs For each wet friction material of Example 1-2 obtained in the above [1] and Comparative example 1 obtained in the above [2] After impregnating the base material with a phenolic resin, the base material for wet friction material impregnated is joined by pressure heating to both the front and back of a flat ring-shaped core plate made of metal (outer diameter 140 mm, inner diameter 110 mm). , The wet friction material for evaluation was obtained.
Using 3 pieces of each of the above wet friction materials for evaluation, using an SAE friction tester (SAE # 2), rotation speed 4000rpm, contact pressure 0.7MPa, oil temperature 100 ° C, oil amount Is: 0.343kg / m The measurement of μs was performed under the condition of ³ (full immersion). The results are shown in Table 1.

From the result of the measurement of μs, in Examples 1 to 3 of the present invention, even if the content of the granular material as the friction modifier in the wet friction material substrate is significantly reduced, it is substantially the same as Comparative Example 1 which is the conventional product. It became clear that the coefficient of static friction of

<2> Measurement of μ-V An LVFA test machine using three pieces of the wet friction material of each of Examples 2 to 3 obtained in the above [1] and the comparative example 1 obtained in the above [2]. The μ-V was measured under the conditions of a rotation speed of 0-1000-0 rpm, a surface pressure of 0.7 MPa, an oil temperature of 40 ° C., and an oil amount of 1000 mL / min. The results are shown in Table 2.

From the result of the measurement of μ-V, as shown in Table 1, in Example 3, although the content of the particulate matter can express at least the excellent coefficient of static friction significantly, in the measurement of μ-V, Comparative Example 1 and It can be seen that the same result remains. On the other hand, in Example 2, as shown in Table 1, in addition to the fact that the content of the particulate matter can at least significantly develop the excellent static friction coefficient, the gradient is a positive gradient compared to Comparative Example 1 which is the conventional product. It can be seen that the μ-V characteristic is improved.

(3) Comparison of Surface Conditions Comparing FIG. 2 (Example 1) and FIG. 4 (Comparative Example 1), even if Example 1 significantly reduces the compounding amount, it is possible to use fibers as in conventional paper making as in conventional papermaking. It has become clear that substantially the same amount of particles as the wet friction material base material produced can be disposed on the friction surface of the wet friction material base material.
Furthermore, when FIG. 2 (Example 1) and FIG. 3 (Example 3) are compared, when the granular material is applied to the formed fiber layer without foaming it (non-foamed coating), the fibers of the fiber layer 11 are The particulate matter 121 clogs the pores 111 formed in (Example 3), but when it is formed into a foam and applied (foam coating), the particulate matter does not exist inside the fiber layer 11 and the pores 111 are not clogged. It can be seen that (Example 1).
From the surface observation and evaluation results of the examples and comparative examples described above, according to the present invention, the friction surface of the fiber layer is treated as a granular layer without using waste particles such as friction modifiers in the conventional fiber layer. It is made to adhere to one side which becomes a side, and, thereby, desired characteristics, such as a frictional characteristic, can be expressed on a frictional surface. At this time, the granular layer does not close the pores on the friction surface side of the fiber layer, has desired pores, and can maintain the same oil absorption as that of the conventional product with respect to the lubricating oil. Therefore, the base material for wet friction materials of the present invention can easily obtain desired properties on the friction surface of the base material for wet friction materials by significantly reducing the compounding amount of the particulate matter, improving the performance, reducing the weight, Enables cost reduction.

  In the present invention, the present invention is not limited to the specific examples described above, and various changes may be made within the scope of the present invention according to the purpose and application.

  The application of the wet friction base material and the wet friction material of the present invention is not particularly limited. Among these, as an automobile article, it is suitably used for an automatic transmission (automatic transmission, AT).

1; Wet friction substrate,
11; fiber layer, 111; pores, 112; fiber,
12; granular layer, 121; granular material.

Claims (4)

And a particulate layer having pores formed by particulate matter on one surface of the fibrous layer.
The particulate layer having pores is formed by adhering to the fibers of the one surface of the fiber layer ,
And, a wet friction material characterized that you have obtained foam is foam breaking the said foam composition containing particulates from foam coating layer, wherein the obtained coated on one surface of the fibrous layer Base material.   The substrate for a wet friction material according to claim 1, wherein the granular material includes a friction modifier. The thickness of the said fiber layer is 0.2 mm or more and 1.3 mm or less, The wet friction material of Claim 1 or 2 characterized by the above-mentioned. A foamy coating layer forming step of applying a foamy composition containing particulate matter to one surface of the formed fiber layer to form a foamy coating layer containing the particulate matter;
And b) a foam-breaking step of breaking the foam constituting the foam-like coating layer to form a particulate layer having pores.